Metal additive manufacturing processes have been widely studied during the last decades. The principle is the superposition of material layers by layers, via specific path in order to produce the desired shape. For wide parts, WAAM – wire arc additive manufacturing – process presents key advantages as low cost investment and already existing raw materials. However, some issues such as the control of component dimensions, internal stresses and microstructures remain to be investigated to allow an extensive use of this process.

This work aims at improving the knowledge of the relations between the parameters of the WAAM process, the associated heat transfer, and the geometrical and microstructural characteristics of the produced samples. The retained material is a 316L stainless steel, extensively used in petrochemical or in marine engineering.

The arc welding technology used in this study is the CMT (Cold Metal Transfer) technology developed by Fronius company, derived from the conventional MIG/MAG process. This technology allows a precise control of the heat input and the deposit of molten metal. Using an instrumented WAAM device, the effect of the numerous process parameters on the current and voltage waveforms controlling the electric arc characteristics, the temperature fields and the deposit of molten metal are investigated. Their management allows a better control of the process and the final shape and metallurgy of the parts. Finally, the parts produced are characterized via microstructural and DRX analyses. The solidification conditions of this austenitic material and the subsequent thermal cycles impact on metallurgy are discussed with respect to the process parameters.